1. Microbiology of Water & Air
Dr.Rouchelle Tellis
Assoc Prof, Microbiology

2. Potable water Clear, colorless, without dis-agreeable taste & odour
Safe: free from harmful toxins & pathogenic Micro-organisms

3. Lesson plan
Water-borne diseases
Pathogen indicators
Coliform bacteria
Streptococcus
Enterococcus
Enumeration Methods
Membrane filter
Presumptive coliform count
Differential coliform count
Surface Water Standards

4. 1991 Cholera Epidemic 1,000,000 cases/10,000 deaths
Water borne pathogens
1991 Cholera Epidemic 1,000,000 cases/10,000 deaths
Bacteria
Virus
Protozoa
Helmiths

5. Bacteria pathogens in water
Enteritis, diarrhea, and dysentery
Campylobacter
V. cholera
E. coli 0157:H
Salmonella, Shigella
Enteric fever: Typhoid, Paratyphoid
Paralysis: Botulism
Eye, ear, skin infections: P.aeruginosa,
M.marinum

6. Viral pathogens in water
Enteritis, diarrhea, and dysentery
Rotavirus, Enterovirus
Norwalk
Hepatitis:
Hepatitis A
Hepatitis E
Paralysis
Polio

7. Protozoa
Giardia
Cryptosporidia
Amoeba

8. Helmith
Round worm
Tape worm
Whip worm

9. Indicator Organisms
General coliforms – indicate water in contact with plant or animal life (universally present)
Fecal coliforms – mammal or bird feces in water
Fecal streptococci– feces from warm blooded animals
Clostridium perfringens

10. Water sample Collection
Routine and regular exercise: Appropriate sterile sampling container with Sodium thio-sulphate to inactivate residual chlorine
Deliver to laboratory soon, not later than 6 hours
Maintain records

11. Coliform Group (total coliform)
Enterobacteriaceae
Facultative anaerobe
Gram negative
Non-spore forming
Rod shaped
Ferment lactose
Produce gas and acid within C
Coliform genera
Enterobacter
Klebsiella
Citrobacter
Escherichia

12. Coliform Group Total coliform Thermo-tolerant Fecal coliforms
Grows at 44.5 C
Escherichia coli
Individual species
Enzyme specific
total coliform
fecal coliform
E. coli

13. Streptococcus and Enterococcus
Fecal Strep
S. faecalis
S. faecium
Resistant to 450C, 40% bile, potassium tellutite & Sodium azide
Fecal Streps that survive in 6.5% sodium chloride

14. Plate count
No. of colonies formed in nutrient agar pour plate cultures of water samples are counted
Incubated aerobically parallel at 370C and 220C
Plate count at 370C:
indicator of fecal pollution
With potentially pathogenic
bacteria

15. Membrane Filter Method:
Filter water through a 0.45 μM membrane filter
Place membrane on selective media
Incubate
350 C total coliform
44.50 C fecal coliform
Count the No. of colonies

16. Presumptive coliform count: Multiple Tube Fermentation Method
An estimate of the No. of coliforms is made by adding varying quantities of water ( ml) to bile salt lactose peptone water or double strength Mac Conkey broth.
Acid and gas formation indicates coliform growth
Probable No. of coliforms per 100 ml is read from Most-Probable-Number (MPN) table of McCardy.

18. Differential coliform count- Eijkman test
To find out whether the coliforms detected in presumptive test are E.coli.
After usual presumptive test, subcultures are made from all the bottles showing acid and gas production to fresh tubes of single strength MA broth, incubated at 440 C .
Thermo-tolerant E. coli give definite proof of fecal pollution.
Those showing gas in Durham’s tubes, contain E.coli.
Confirmation of E.coli can be done by testing for indole production and citrate utilization.

19. Enzyme Substrate or Chromogenic Substrate Method
Total coliforms have the enzyme
β-D-galactosidase which hydrolyses ortho-nitrophenyl- β-D-galactopyranoside (ONPG)
Yellow when hydrolyzed
E. coli has the enzyme
β-glucuronidase which hydrolyses 4-methylumbelliferyl-β-glucuronide (MUG)
Fluoresces when hydrolyzed

20. ONPG-Total Coliform
MUG- E. coli

21. Chlorination of Water

22. Methods of Treatment
Shock Chlorination ( ppm, contact of at least 6 hours)
Continuous Chlorination – for recurring bacterial contamination problems – a measurable amount of free residual chlorine

23. Kill Inorganic Free Residual Chlorine Organic Chlorine Dosage Combined
Demand
Kill
Free
Residual
Chlorine
Combined
Residual
Chlorine
Organic

24. Bacteriology of Air
Air borne infections: transmission of infection produced by respiratory droplets less than 5um in size
Droplet infection: Transmission of infection produced by respiratory droplets larger than 5um in size
Pathogenic bacteria do not multiply in air

25. Pathogenic organisms spread through air
Bacterial:
Streptococcus pyogenes
M.tuberculosis
N.meningitidis
C.diphtheriae
H.influenzae type B
B.pertussis
Y.pestis (pneumonic plague)
Mycoplasma pneumoniae

26. Viral infections that spread through air:
Influenza viruses
Rubella virus
Mumps virus
Adenovirus
Parvo-virus B19

27. Mechanism of spread of infection
Droplets and droplet nuclei while coughing, sneezing and talking

28. Measurement of air contamination
Sedimentation ‘Settle Plate method’
Estimating the No. of bacteria in air by permitting bacteria to settle on open perti dishes containing culture media over a fixed duration.

29. Slit sampler
A means of estimating the No. of bacteria present in the air by passing a known volume of air through the ‘slit’ 0.25mm wide.
Air is directed onto a pate
and mechanically rotated